When feeding the sheet material conveyed by the stacker into the press machine, it is necessary to correspond the centre or a predetermined point of the sheet material with the centre of the press machine and correspond the position of the sheet material with the stroke of feed thereof to the press machine. To achieve this, a sheet material positioning apparatus has so far been located between the destacker and the press machine.
For example, as disclosed in Japanese Patent Publication No. 54-11190, Japanese Utility Model Application Laid-open Specification No. 57-11635, Japanese Patent Application Laid-open Specification No. 59-24537, and further in Japanese Patent Application Laid-open Specification No. 61-38725, etc., a sheet material positioning apparatus is known which comprises a body frame having a pair of side guides, at least a front gauge and at least a rear gauge mounted, respectively, on the body frame, the arrangement being made such that the centering of a sheet material is made by these pair of side guides to correspond the centre of the sheet material with that of the press machine and the position of the sheet material in the feeding direction is controlled by the front and rear gauges.
Such a conventional sheet material positioning apparatus has been disadvantageous in that, since the above-mentioned pair of side guides are disposed oppositely and in parallel relationship in the direction at right angles to the sheet material feeding direction and arranged to be moved towards and away from each other, the sheet materials which can be subjected to centering are limited only to those whose both side surfaces in the feeding direction are parallel, and therefore centering of sheet materials of various configurations can not be made.